Values are mean (SD) or (%). ∞All patients imply results for all patients with the C3c measurement, including the only one with the diminished C3c value. * value < 0.05 in Mann-Whitney test, the comparison between the group with normal C3c and elevated C3c. °Heart rate according to electrocardiogram. †Comorbidities: atrial fibrillation: diagnosed from the electrocardiogram. Hypertension: sitting blood pressure > 140/90 mmHg or history of hypertension prior to the onset of heart failure or hypertensive heart disease accepted as predominant cause of heart failure. COPD: chronic obstructive pulmonary disease: history of this condition requiring bronchiolytic treatment or newly diagnosed according to the Global Initiative for Chronic Obstructive Lung Disease criteria [43]. Anemia according to WHO criteria: haemoglobin <12 g/dL in women and <13 g/dL in men [44]. Renal dysfunction: estimated glomerular filtration rate < 60 mL/min/1.73 m² [45]. ICD: implantable cardioverter-defibrillator. CRT: cardiac resynchronization therapy with a biventricular defibrillator; ACEi: angiotensin-converting enzyme inhibitor; ARB: angiotensin receptor blocker.